"But no smothering," he warned, instructing gardeners to drive bamboo or stakes in the ground around the plant to support a makeshift tent and then place rocks or something heavy at the bottom to prevent the sheet from blowing off.

Never substitute the sheet with a plastic bag, he said.

For more vulnerable species such as rosebushes, it helps to pack the base with compost.

Barrett said gardeners should avoid insulating the base of bushes or shrubs with dead leaves, which can spread disease to the plants.

And although it's a good idea to remove dead leaves, wait to prune until the weather starts to warm up.